Immunohistofluorescence Localization of Histamine and Histamine Receptors in Ganglia and Tissues of the Bivalve Mollusc, Crassostrea virginica

Abstract

Histamine (HIS), a biogenic amine is a neurotransmitter in nervous systems and in sensory receptors in a variety of invertebrates rarely has been reported in bivalves. We showed it is involved in sensory reception in sensory‐motor integration of gill lateral cell cilia beating in the bivalve, Crassostrea virginica and used HPLC to show it present in ganglia and tissues. We hypothesize HIS neurons and HIS receptors are present in ganglia and innervated tissue of C. virginica. We tested this with immunohistofluorescence using 1̊ antibodies to HIS and HIS receptors, and fluorescently labeled 2̊ antibodies. Tissues were dissected, snap frozen, cryostat sectioned, fixed with EDAC (N‐Ethyl‐N'‐(3‐dimethylaminopropyl) carbodiimide hydrochloride) or paraformaldehyde, treated with blockers, and incubated with 1̊ then 2̊ antibodies. Whole mounts of gill and mantle also were similarly treated visualized. Results show HIS and HIS H2 receptors in visceral ganglia, gill, mantle body and sensory tentacles of mantle rim. Of particular significance is their presence in sensory tentacles as that correlates well with our previous sensory physiology studies, and their presence in gill interfilamental junctions, the physiology of which has not been well described. The project confirms the identity of HIS and H2 receptors in the nervous system and innervated organs, and coupled with our other work shows HIS to be an important endogenous biogenic amine in the bivalve C. virginica.